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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Switch with neon indicator
I've got some lights in the loft with the switch in the passageway
below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson |
#2
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Switch with neon indicator
Kit Jackson wrote:
Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? In the past I've had touch dimmers that had a neon which worked without a neutral, back in the days of incandescent lamps they probably were able to pull enough current from neutral through the lamp, probably not these days with CFLs. Or just maybe they treated the earth as a "neutral" a bit naughty as it would tip an RCD a few mA more towards tripping. |
#3
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Switch with neon indicator
On 20/10/16 22:54, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. Drill a small hole in the loft door? -- Adrian C |
#4
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Switch with neon indicator
On Thursday, 20 October 2016 23:06:55 UTC+1, Andy Burns wrote:
Kit Jackson wrote: Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? In the past I've had touch dimmers that had a neon which worked without a neutral, back in the days of incandescent lamps they probably were able to pull enough current from neutral through the lamp, probably not these days with CFLs. Or just maybe they treated the earth as a "neutral" a bit naughty as it would tip an RCD a few mA more towards tripping. The switch has live & switched live, so the neon would be on when lights off, wrong way round. OP needs a neutral, assuming not going to connect neon to earth. Earth return isn't allowed, though with a [suitable] stack of resistors the risk would be pretty much zero. Or maybe mount a neon into the ceiling, its wiring then being in the loft. NT |
#6
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Switch with neon indicator
If you are goint to do the latter, you could probably use an led and some
little circuit to bleed of just enough th run the little led, but its a bodge. Brian -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! wrote in message ... On Thursday, 20 October 2016 23:06:55 UTC+1, Andy Burns wrote: Kit Jackson wrote: Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? In the past I've had touch dimmers that had a neon which worked without a neutral, back in the days of incandescent lamps they probably were able to pull enough current from neutral through the lamp, probably not these days with CFLs. Or just maybe they treated the earth as a "neutral" a bit naughty as it would tip an RCD a few mA more towards tripping. The switch has live & switched live, so the neon would be on when lights off, wrong way round. OP needs a neutral, assuming not going to connect neon to earth. Earth return isn't allowed, though with a [suitable] stack of resistors the risk would be pretty much zero. Or maybe mount a neon into the ceiling, its wiring then being in the loft. NT |
#7
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Switch with neon indicator
On 20/10/2016 22:54, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. As an aside this reminds me of the hotel owners that went into their attic to thaw frozen pipes with an electric heater only to find one already there and switched on... From when the pipes froze 8 years before! Mike |
#8
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Switch with neon indicator
On 21/10/2016 08:25, Brian Gaff wrote:
Not really or reliably, Is there an earth present? Sounds like a bit of dodgy wiring to me. Brian If you don't mind the lit neon indicating the loft lights are *NOT* on then you can wire the neon indicator in parallel with the switch. Otherwise you need a local neutral from somewhere. Deliberately adding earth leakage current isn't a good idea. -- Regards, Martin Brown |
#9
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Switch with neon indicator
On 20/10/2016 22:54, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers -- Syd |
#10
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Switch with neon indicator
On 21/10/2016 09:29, Syd Rumpo wrote:
On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers Like this, perhaps... https://www.youtube.com/watch?v=JxpERETpqfI He's used just one LED, which isn't great, LEDs shouldn't have reverse current through them, but the clip-on core idea is good. Cheers -- Syd |
#11
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Switch with neon indicator
On 20/10/2016 22:54, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be be present? Kit Jackson If the switch cable goes straight up from the switch to the loft it might not be that difficult to replace it with a 3 core and earth cable. You could see if the cable can move a little -- Michael Chare --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#12
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Switch with neon indicator
On 21/10/16 09:40, Syd Rumpo wrote:
On 21/10/2016 09:29, Syd Rumpo wrote: On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers Like this, perhaps... https://www.youtube.com/watch?v=JxpERETpqfI He's used just one LED, which isn't great, LEDs shouldn't have reverse current through them, but the clip-on core idea is good. and he can detect an electric fire, but not necessarily a lightbulb. Fora fixed installation I see no reason why a very small mains transformer used backwards - i.e. with the low voltage winding in series with the switched load - would not work as well. Cheers -- The theory of Communism may be summed up in one sentence: Abolish all private property. Karl Marx |
#13
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Switch with neon indicator
"Syd Rumpo" wrote in message ... On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers -- Syd That's a great idea. It could be done without a transformer. Assuming one 60W incandescent bulb in the loft, it takes 250mA. Six 1 amp diodes wired as three back-to-back pairs all in series with the switched live, would drop about 1.5V and dissipate 0.6W overall per bulb. Wire a LED in series with a 470 ohm resistor across the diode array, to give about 2mA into the LED. If there are other bulbs in the loft, use LED types to keep the overall current down. Of course house all the components in an insulated box. -- Dave W |
#14
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Switch with neon indicator
On 21/10/2016 10:33, Dave W wrote:
"Syd Rumpo" wrote in message ... On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers -- Syd That's a great idea. It could be done without a transformer. Assuming one 60W incandescent bulb in the loft, it takes 250mA. Six 1 amp diodes wired as three back-to-back pairs all in series with the switched live, would drop about 1.5V and dissipate 0.6W overall per bulb. Wire a LED in series with a 470 ohm resistor across the diode array, to give about 2mA into the LED. If there are other bulbs in the loft, use LED types to keep the overall current down. Of course house all the components in an insulated box. I like that. Maybe use 4 diodes, one in inverse parallel with a string of three in series to further reduce dissipation. Or a single 1.8V Zener, if you can find one. Cheers -- Syd |
#16
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Switch with neon indicator
On Thursday, 20 October 2016 22:54:07 UTC+1, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Buy yourself a light switch illuminator. Requires no neutral. But may need an incandescent lamp. http://www.builderdepot.co.uk/mk-neo...etbRoC8nrw_wcB They are on when the light is off however. |
#17
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Switch with neon indicator
On 10/21/2016 9:09 AM, Martin Brown wrote:
On 21/10/2016 08:25, Brian Gaff wrote: Not really or reliably, Is there an earth present? Sounds like a bit of dodgy wiring to me. Brian If you don't mind the lit neon indicating the loft lights are *NOT* on then you can wire the neon indicator in parallel with the switch. Otherwise you need a local neutral from somewhere. Deliberately adding earth leakage current isn't a good idea. Lateral thinking! I like it! |
#18
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Switch with neon indicator
On Friday, 21 October 2016 18:45:43 UTC+1, harry wrote:
On Thursday, 20 October 2016 22:54:07 UTC+1, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Buy yourself a light switch illuminator. Requires no neutral. But may need an incandescent lamp. http://www.builderdepot.co.uk/mk-neo...etbRoC8nrw_wcB They are on when the light is off however. |
#19
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Switch with neon indicator
On 21/10/2016 09:09, Martin Brown wrote:
Otherwise you need a local neutral from somewhere. Providing that "somewhere" is on the same circuit. Borrowed neutrals can cause problems. -- Mike Clarke |
#20
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Switch with neon indicator
"Syd Rumpo" wrote in message ... On 21/10/2016 10:33, Dave W wrote: "Syd Rumpo" wrote in message ... On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers -- Syd That's a great idea. It could be done without a transformer. Assuming one 60W incandescent bulb in the loft, it takes 250mA. Six 1 amp diodes wired as three back-to-back pairs all in series with the switched live, would drop about 1.5V and dissipate 0.6W overall per bulb. Wire a LED in series with a 470 ohm resistor across the diode array, to give about 2mA into the LED. If there are other bulbs in the loft, use LED types to keep the overall current down. Of course house all the components in an insulated box. I like that. Maybe use 4 diodes, one in inverse parallel with a string of three in series to further reduce dissipation. Or a single 1.8V Zener, if you can find one. Cheers -- Syd Yes you are right. You might get away with only two diodes in the forward direction and one in reverse, and a lower value of resistor. I've now had an even better idea. Put a 12V 5W festoon car bulb in series with the live circuit. Such a bulb normally takes about half an amp in the car, so 250mA would generate only 6V across it, leaving the rest of the mains voltage for the 60W bulb, and might glow nicely especially if behind a red filter. -- Dave W |
#21
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Switch with neon indicator
On Fri, 21 Oct 2016 22:08:51 +0100, Dave W wrote:
"Syd Rumpo" wrote in message ... On 21/10/2016 10:33, Dave W wrote: "Syd Rumpo" wrote in message ... On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers -- Syd That's a great idea. It could be done without a transformer. Assuming one 60W incandescent bulb in the loft, it takes 250mA. Six 1 amp diodes wired as three back-to-back pairs all in series with the switched live, would drop about 1.5V and dissipate 0.6W overall per bulb. Wire a LED in series with a 470 ohm resistor across the diode array, to give about 2mA into the LED. If there are other bulbs in the loft, use LED types to keep the overall current down. Of course house all the components in an insulated box. I like that. Maybe use 4 diodes, one in inverse parallel with a string of three in series to further reduce dissipation. Or a single 1.8V Zener, if you can find one. Cheers -- Syd Yes you are right. You might get away with only two diodes in the forward direction and one in reverse, and a lower value of resistor. I've now had an even better idea. Put a 12V 5W festoon car bulb in series with the live circuit. Such a bulb normally takes about half an amp in the car, so 250mA would generate only 6V across it, leaving the rest of the mains voltage for the 60W bulb, and might glow nicely especially if behind a red filter. Tungsten filament lamps have a very high positive temperature coefficient of resistance. Typically, the hot resistance is an order of magnitude greater than its cold resistance for ordinary tungsten filaments running in an evacuated envelope such as that festoon lamp. Halving the current doesn't simply drop the voltage to half, more likely to one quarter or less. Indeed, using that lamp as envisaged, you may not even be able to see it glow at all without peering very closely at the naked lamp whilst shading it from any bright room lighting. The use of a LED lamp with a fullwave bridge rectifier plus 4 or 5 silicon diodes in series across the DC output and a series current limiting resistor for the LED itself wired across the resulting voltage clipped rectifier output is a far better idea if you don't mind losing 4 or 5 volts from the lamp supply. However, the best version of this "Current Flow Detector" wired in series with the lamp switched live (on ac supplies) is the already proposed use of a current transformer. If you're going to go to the trouble of using the CT option, choose the turns (or current) ratio carefully so that the indicator LED will glow just as brightly with a 10W LED lamp as it will with that 60W incandescent lamp you mentioned. Assuming a high quality 10W LED (the 810 Lm equivalent of the American 60W incandescent 120v 750 hour rated lamp, aka the 75W 230v 1000 hour UK/ European equivalent), you'd be looking at a line current of 42mA at unity power factor. That's your worst case condition. In all probability, you'll fit a cheap as chips (fvsvo 'cheap') lamp using a simple "capacitive dropper" ballast circuit with a PF figure the wrong side of the 50% mark resulting in a current more in the region of 80 to 100mA. If we assume the "worst case scenario" from the point of view of guaranteeing a minimum lumens output from our indicator LED then we only need to decide on how much current will prove sufficient to allow the indicator LED to meet this minimum illumination level. Depending on the desired brightness and efficiency of the LED, you're probably looking at an indicator LED current in the region of 1 to 10mA[1]. If you assume the upper figure the CT ratio would need to be a minimum of 4:1 which quite frankly, seems rather a low ratio for a CT. A few years back, I modded the mains sockets fed from my UPS protected supply to provide a "Power Present" indicator lamp. I used vintage (at least two decades old at the time) 3mm dia red LEDS wired in anti-parallel with a cheap 1A silicon diode with a small capacitor and an inrush limiting resistor in series with the LED wired across the Live and neutral. ISTR using a 47nF cap with a 2K2 half watt resistor for the capacitive volt dropper. When I tentatively checked out the impedance of a 100nF cap by way of a 'sanity check' to jog my memory just now, I was looking at a reactance value at 50Hz of just 32K ohm (just over 7mA's worth if true) so I'm pretty certain I'd have used the more space saving value of 47 or possibly even 33 nF. Bearing in mind that the LED only sees half of the current cycles in this simple circuit I'm looking at an average current of just 1.75mA (or possibly even just over 1mA with a 33nF cap). These vintage red LEDs provide a more than bright enough indication so I rather suspect a mere one mA will more than suffice using modern higher efficiency indicator LEDs with a fullwave rectifier. If we assume a 1mA current in the secondary of the CT, this allows the use of a 40:1 CT, a more typical turns ratio value for an off the shelf CT imo. :-) The original circuit (F/W rect with 4 or 5 voltage clamping diodes (or 3v3 zenner diode) feeding a LED via a current limiting resistor) is simply wired across the low current secondary of the CT and the primary wired in series with the live feed to the lamp. Instead of losing 5 volts or so, you'll only lose 125mV across the CT's high current primary. Furthermore, the rectifier and voltage clamping diodes need only handle one fortieth of the lamp current which is a bonus when it comes to coping with short circuit fault currents. You might even be able to make your own CT using a ferrite ring with 20 to 40 turns of fine (28 SWG?) enamelled copper wire wound onto the ring which can then be threaded onto the switched live conductor, neatly avoiding having to insert an extra connector into the circuit. :-) If you have a suitable ferrite ring and the yard or two of fine enamelled copper wire to hand, you can build a test circuit and test with a suitable lamp holder wired to a 13A plug (I'm assuming the indicator LED and other components won't be a problem for you to source). There's just one final note: You may find this CT based current indicator possibly a little too sensitive to fully extinguish when the light is switched off. If this turns out to be the case, just wire another resistor (10K?) across the rectifier output pins to divert this 'nuisance current' around the LED part of the circuit. [1] That was a ball park guess which, on reflection (that memory jogging exercise re the average current in those power present indicator LEDS) was rather on the high side even for vintage LED indicator lamps, let alone the more efficient indicator LEDs available today. If you don't mind the painful brightness of blue LEDs you can reckon on only needing a tenth of the current required by a red LED. -- Johnny B Good |
#22
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Switch with neon indicator
On 20/10/2016 22:54, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? There is no obvious way of doing it with a neon, but you could do it with an LED. If you took say 4 silicon rectifier diodes, and arranged them so that you have three of the silicon diodes in series with the switched live, then the fourth in parallel with them but reversed in direction, you should have a bi-directional current path through the switch and the lamp(s). Now wire LED with a series current limiting resistor across the three silicon diodes, and there should be sufficient voltage drop across the silicon diodes to forward bias the LED and cause it to light. (The LED will be in effect running from a half wave rectified supply, so you may see some flicker on it. This could be more pronounced if the load you are switching is a low energy lamp rather than an incandescent You could add a smoothing cap if that is a problem) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#23
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Switch with neon indicator
Why not just add an extra light - as a downlight in the ceiling below - that is on the same circuit as the loft lights. It will be an easy prompt to turn them off. |
#24
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Switch with neon indicator
"Johnny B Good" wrote in message ... On Fri, 21 Oct 2016 22:08:51 +0100, Dave W wrote: "Syd Rumpo" wrote in message ... On 21/10/2016 10:33, Dave W wrote: "Syd Rumpo" wrote in message ... On 20/10/2016 22:54, Kit Jackson wrote: I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Feed the live through a current transformer primary with a pair of inverse parallel LEDs on the secondary. Winding details are left to the student. Cheers -- Syd That's a great idea. It could be done without a transformer. Assuming one 60W incandescent bulb in the loft, it takes 250mA. Six 1 amp diodes wired as three back-to-back pairs all in series with the switched live, would drop about 1.5V and dissipate 0.6W overall per bulb. Wire a LED in series with a 470 ohm resistor across the diode array, to give about 2mA into the LED. If there are other bulbs in the loft, use LED types to keep the overall current down. Of course house all the components in an insulated box. I like that. Maybe use 4 diodes, one in inverse parallel with a string of three in series to further reduce dissipation. Or a single 1.8V Zener, if you can find one. Cheers -- Syd Yes you are right. You might get away with only two diodes in the forward direction and one in reverse, and a lower value of resistor. I've now had an even better idea. Put a 12V 5W festoon car bulb in series with the live circuit. Such a bulb normally takes about half an amp in the car, so 250mA would generate only 6V across it, leaving the rest of the mains voltage for the 60W bulb, and might glow nicely especially if behind a red filter. Tungsten filament lamps have a very high positive temperature coefficient of resistance. Typically, the hot resistance is an order of magnitude greater than its cold resistance for ordinary tungsten filaments running in an evacuated envelope such as that festoon lamp. Halving the current doesn't simply drop the voltage to half, more likely to one quarter or less. Indeed, using that lamp as envisaged, you may not even be able to see it glow at all without peering very closely at the naked lamp whilst shading it from any bright room lighting. Yes I know. That's why I said "might glow". If it's not visible, try using more than 60W in the loft (we don't know what the OP has), or a lower wattage 12V bulb. I've just tried a 6V 5W festoon bulb on a controlled current supply, taking 0.8A. When reduced to 0.4A the voltage across it was only 1V. So my post should have said 2V not 6V. However my result was a visible glow similar to a neon. lecture snipped -- Dave W |
#25
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Switch with neon indicator
In article ,
Brian Gaff wrote: If you are goint to do the latter, you could probably use an led and some little circuit to bleed of just enough th run the little led, but its a bodge. LEDs generally need about 10mA to be decently bright. Not sure I'd want that deliberately flowing on an RCD protected circuit. -- *You are validating my inherent mistrust of strangers Dave Plowman London SW To e-mail, change noise into sound. |
#26
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Switch with neon indicator
On 20/10/2016 22:54, Kit Jackson wrote:
Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Construct a current transformer with a clip on ferrite 'suppression' core with a led and diode across the output. -- mailto: news {at} admac {dot] myzen {dot} co {dot} uk |
#27
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Switch with neon indicator
alan_m wrote:
On 20/10/2016 22:54, Kit Jackson wrote: Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Construct a current transformer with a clip on ferrite 'suppression' core with a led and diode across the output. Have you actually tried that? I've not either but I would suspect the ferrite designed for suppression would not have much response at 50Hz. Happy to be educated otherwise if it works. |
#28
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Switch with neon indicator
On Saturday, 22 October 2016 13:48:54 UTC+1, Dave Plowman (News) wrote:
In article , Brian Gaff wrote: If you are goint to do the latter, you could probably use an led and some little circuit to bleed of just enough th run the little led, but its a bodge. LEDs generally need about 10mA to be decently bright. Not sure I'd want that deliberately flowing on an RCD protected circuit. 1970s LEDs maybe. NT |
#29
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Switch with neon indicator
On 20 Oct 2016 21:54:05 GMT, Kit Jackson wrote:
I've got some lights in the loft with the switch in the passageway below. It's not unknown for the loft lights to be left on all night or even all weekend if I don't notice the switch. I'd like to replace the switch with one that has a neon indicator. The problem is that the lights have been wired with a loop-in circuit so that the power runs from ceiling rose to ceiling rose and only the switched live is taken down to the light switch. The neon switch I've got seems to require the neutral to be present as the neon is soldered between the live and neutral on the load side of the switch. Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Why not just put the switch in the loft? --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#30
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Switch with neon indicator
On 2016-10-22 15:21:13 +0000, ARW said:
On 20 Oct 2016 21:54:05 GMT, Kit Jackson wrote: Is there any way to wire this so the a neon switch would work without the need to drop another cable from the rose to the switch? Or can you get neon switches that will work without the need for the neutral to be present? Kit Jackson Why not just put the switch in the loft? Wire it between live and earth if the rcd, if any, will take it. |
#31
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Switch with neon indicator
In article ,
wrote: On Saturday, 22 October 2016 13:48:54 UTC+1, Dave Plowman (News) wrote: In article , Brian Gaff wrote: If you are goint to do the latter, you could probably use an led and some little circuit to bleed of just enough th run the little led, but its a bodge. LEDs generally need about 10mA to be decently bright. Not sure I'd want that deliberately flowing on an RCD protected circuit. 1970s LEDs maybe. I was assuming it needed to be clearly visible in bright light. -- *Lawyers believe a man is innocent until proven broke. Dave Plowman London SW To e-mail, change noise into sound. |
#32
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Switch with neon indicator
On Sunday, 23 October 2016 00:34:15 UTC+1, Dave Plowman (News) wrote:
In article , tabbypurr wrote: On Saturday, 22 October 2016 13:48:54 UTC+1, Dave Plowman (News) wrote: In article , Brian Gaff wrote: If you are goint to do the latter, you could probably use an led and some little circuit to bleed of just enough th run the little led, but its a bodge. LEDs generally need about 10mA to be decently bright. Not sure I'd want that deliberately flowing on an RCD protected circuit. 1970s LEDs maybe. I was assuming it needed to be clearly visible in bright light. Modern LEDs are IME visible indoors in daylight on very little current. Even mid 1980s LEDs were normally visible on 10mA indoors. NT |
#33
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Switch with neon indicator
Don't risk leaving behind a bodge if you die! It will spoil your reputation. (I still worry about the neon I bridged to earth in a room thermostat that didn't have a neutral) |
#34
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Switch with neon indicator
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#35
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Switch with neon indicator
In article ,
alan_m wrote: On 23/10/2016 03:01, wrote: Modern LEDs are IME visible indoors in daylight on very little current. Even mid 1980s LEDs were normally visible on 10mA indoors. I have recently fitted a couple of 5mm green LEDs to an outdoor wall plaque and running at 500uA from a battery they are visible outdoors on a sunny day. At night they are way too bright and this week I may reduce the current. OK. I've not got any near that sort of efficiency. Never really been that worried about efficiency for signal types anyway. -- *Marriage changes passion - suddenly you're in bed with a relative* Dave Plowman London SW To e-mail, change noise into sound. |
#36
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Switch with neon indicator
On Sunday, 23 October 2016 18:58:25 UTC+1, alan_m wrote:
On 23/10/2016 03:01, wrote: Modern LEDs are IME visible indoors in daylight on very little current. Even mid 1980s LEDs were normally visible on 10mA indoors. I have recently fitted a couple of 5mm green LEDs to an outdoor wall plaque and running at 500uA from a battery they are visible outdoors on a sunny day. At night they are way too bright and this week I may reduce the current. Any link for these LEDs the lowset current I've seen is 2ma and they aren't all that bright. |
#37
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Switch with neon indicator
On 25/10/2016 09:45, whisky-dave wrote:
On Sunday, 23 October 2016 18:58:25 UTC+1, alan_m wrote: On 23/10/2016 03:01, wrote: Modern LEDs are IME visible indoors in daylight on very little current. Even mid 1980s LEDs were normally visible on 10mA indoors. I have recently fitted a couple of 5mm green LEDs to an outdoor wall plaque and running at 500uA from a battery they are visible outdoors on a sunny day. At night they are way too bright and this week I may reduce the current. Any link for these LEDs the lowset current I've seen is 2ma and they aren't all that bright. Most of the current generation of LEDs are bright enough to see that the die is lit up in daylight with about 10uA flowing. Allowing that much leakage will allow you to find an LED torch in the pitch dark. Once dark adapted you can see by the light it emits on 10uA current. If you want something visible in full sun then you will need a bit more current but modern LEDs are plenty bright enough to do the job. I prefer the 3M glotorch dayglo plastic which can manage to store enough sunlight to illuminate a room for adapted night vision. -- Regards, Martin Brown |
#38
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Switch with neon indicator
On Tuesday, 25 October 2016 22:04:40 UTC+1, Martin Brown wrote:
On 25/10/2016 09:45, whisky-dave wrote: On Sunday, 23 October 2016 18:58:25 UTC+1, alan_m wrote: On 23/10/2016 03:01, wrote: Modern LEDs are IME visible indoors in daylight on very little current. Even mid 1980s LEDs were normally visible on 10mA indoors. I have recently fitted a couple of 5mm green LEDs to an outdoor wall plaque and running at 500uA from a battery they are visible outdoors on a sunny day. At night they are way too bright and this week I may reduce the current. Any link for these LEDs the lowset current I've seen is 2ma and they aren't all that bright. Most of the current generation of LEDs are bright enough to see that the die is lit up in daylight with about 10uA flowing. Allowing that much leakage will allow you to find an LED torch in the pitch dark. Once dark adapted you can see by the light it emits on 10uA current. could you at least link to this magic LED's becaus ethe only refernce I could find wass one pulsed at a much higher current than 10uA closer to 100uA and higher and with a very narrow viewing angle. If you want something visible in full sun then you will need a bit more current but modern LEDs are plenty bright enough to do the job. at a couple of ma yes but nit at uA. I prefer the 3M glotorch dayglo plastic which can manage to store enough sunlight to illuminate a room for adapted night vision. Not much use as indicators though are they. |
#39
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Switch with neon indicator
In article ,
whisky-dave wrote: Most of the current generation of LEDs are bright enough to see that the die is lit up in daylight with about 10uA flowing. Allowing that much leakage will allow you to find an LED torch in the pitch dark. Once dark adapted you can see by the light it emits on 10uA current. could you at least link to this magic LED's becaus ethe only refernce I could find wass one pulsed at a much higher current than 10uA closer to 100uA and higher and with a very narrow viewing angle. Yup. I'd be interested too. I'd be using a large diffused type as a signal which can be seen from a wide range of postions, and want one which was clearly visible in any likely lighting condition. Not much point in having a warning light if you have to go right up to the switch to see it. -- *If at first you don't succeed, then skydiving definitely isn't for you * Dave Plowman London SW To e-mail, change noise into sound. |
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